Electrode for electric arc welding



Oct. 26, 1937. mm ET AL 2,097,386

ELECTRODE FOR ELECTRIC ARC WELDING Filed May 31, 1935 4504 2 z. w a /er"UNITED STATES PATENT OFFICE v 2.097.380 HECTBODE FOR ELECTRIC ABCWELDING Georg Bock and Edmund Sehroder, Berlin, Germany Application May31, 1935, Serial No. 24,408

In Germany August 21, 1934 1 Claim. (Cl. 219-8) This invention relatesto electrodes for electric arc welding and has for its object to providean electrode of this kind which will enable welds to be obtained havingstrength and ductility values and other properties which hitherto havebeen unobtainable or obtainable only with great difllculties.

When it has been intended hitherto to obtain special strength andductility values with weld- 10 ing electrodes, it has been necessarysuitably to alloy the rod for this purpose and to provide it with anenvelope matched to the alloy and intended to bring' this into thewelding bath with as little alteration as possible. Owing to the fact 18that the principal alloy materials, e. g. manganese, and (particularlyfor high strength values) vanadium or molybdenum, burn away to aconsiderable extent during the welding operation, the alloying of thewelding rod had always to be congo siderably higher than was intended tobe achieved in the weld.

It is known, for example, that a rod 4 mm. thick which is to produce inthe bath 01' metal temporarily fused in the welding a strength valueobtain- 25 able with about of manganese, requires an alloy containing 3&% 01' manganese. even it it is surrounded by a thick asbestos envelope.The thick envelope produces the additional defect that thick deposits ofslag are formed upon the weld,

30 and this brings about the limitation that such electrodes can only beutilized for welding almost exclusively in a horizontal position, sothat work having welding seams in several directions must be turned overaccordingly. v

35 To protect the alloy materials from burning it has also been proposedto envelop electrodes in materials which, upon tion, are supposed toevolve a protective gas.

Furthermore, electrodeshave also been provided 40 which were wound withseveral layers otpaper, and again others which were wound with a layeroi'textilematerialandthenimmersedinaslag bath. Alloy materials, e. g.term-manganese, ierro-vanadium and the like, also silicon carbide,

45 have also been added to the welding bath. and

yet only uncertain and varying results have been obtained by all thisconsiderable wasting of aciditional materials.

The invention aii'ords the results aimed at, but

50 not achieved by the known methods, with certitude and without loss 0!materials. Moreover it has the advantage that it melts almost withoutslag formation and may be utilised for welding in any.

position. 66 According to the invention an electrode for electric arcwelding comprises a fusible rod, a gasiilable band carrying alloyablesubstance as a powder in concentrated form secured about the rod by agasiflable adhesive, and a thin covering adapted to serve as a retortopen towards the L welding bath and concentrating the evolved gasesthereon.

The covering layer may consist of a plastic mixture which becomes gastight upon drying, such as finely ground oxide in water glass, withadded 10 substances for stabilizing the arc.

Preferably the band consists of paper or other cellulosic material andis wound helically upon the rod prior to the application of thecovering. The band may be impregnated with substances such as fireprotective substances, e. g. tungstates, for controlling the speed ofgaslflcation of the band.

A typical construction oi the novel electrode is as follows:

A band made of gasiflable material (e. g. paper, or a similar band ofcellulose) is helically wound on the rod slightly to overlap, so thatthe convolutions oi the band width are tightly closed in order to assuregreater density. The band, which is thin, about .03 to .05 mm., or forbaths t6 be carbonized up to'.1 mm. thick, is first covered with a verythin layer of glue (e. g. vegetable glue) or with a very thin layer ofresin, and carries with the aid of this adhesive layer a powdered alloyor -de-oxidizing material, e. g. farm-manganese, va-

nadium or chromium. How little of this is required is shown by the factthat after the application oi the powder the paper loses only about onehalf of its transparency. The band is then wound on the rod with themetal powder in contact with the rod, only a thin stroke of adhesivebeing required to hold the band. Following the winding,

the rod is immersed in a plastic mass which will become gas tight ondrying and renders the outermost layer of paper incombustible, thisbeing achieved by the addition of tungstates or similar fire protectivematerials. Slag envelopes which become porous when solidified are notemployed, except with the addition of substances which will make themgas tight, i. e. materials utilized as solidifying agents which are alsoemployed in colouring materials, e. g. colcothar, ti-' tanium white withadditions oi enamelling clay and the like. As is known in the art ofenamelling, such mixtures form. ii water glass is added, en-

velopes which become gas tight upon drying and remain gas tight in thinflowing molten condition, even it they contain additions to reduce scaleformation, such as potassium nitrate, potassium ss manganate, potassiumhydroxide and so forth. such addition being employed to render theelectrode easily manageable for alternating current and to stabilize theare.

The importance of the closed tubular shape for ,10 the edges of the bandare not closed. then the weld loses very considerably in strength andductility. The doubling of the quantity of the alloy material, or thedoubling of the glue or'paper layer makes no noticeable difference inthis. The tubular gas jet is then no longer closed. The necessity of thegas tight envelope is shown in the same way. If the wound rod isimmersed in masses which have the usual slag composition, then thequality of the weld deteriorates in a similar manner. Increasing theamount of the metal powder is only helpful in the case of quantitiesequal to about 20m 30% of the weight of the envelope, this beingconsiderably thicker. Increasing the quantity of the carbo-hydrate isonly a chance remedy. Moreover, too large quan- I titles of gas evolversburst the strongest envelopes. The band, as already mentioned, is woundto overlap to assure with certitude that the tubular jet always remainsclosed.

An electrode constructed as aforesaid will produce with normal,unalloyed iron wire:-

Ductilities of 28-32%,

A bending angle of 180,

A strength of 48 to 65 kg. per square millimetre.

36 Moreover, the weld is forgeable to needle fineness and the electrodemelts with freedom from slag and may be used for welding in anyposition.

Hitherto these results were considered to be altogether impossible ofachievement with an 40 electrode containing a small amount of slag.

The electrode may be produced by machinery (winding machines) withperfect uniformity and it may be stored and shipped more readily thanthe known jacketed ones, while in addition it is 45 cheaper and moreeconomical.

In order that the differences between the new electrode and the knownones may be brought out more clearly, reference is made to theaccompanying drawing.

4 60 Figs. 1 and 2 are views partly in section of two known types ofelectrodes.

Figs. 3 and 4 are similar views of two forms of electrodes constructedin accordance with the invention.

66 Fig. 1 of the drawing shows on an enlargedscale an electrode of knownconstruction. namely a rod enveloped in several layers of paper band.The layers of paper band are usually stuck together by water glass. Eindicates the electrode for the purpose of surrounding the whoieweldingzone by protective gas. It will now be shown why this result could neverbe achieved with certainty.

The drop T usually starts with a diameter which 70 corresponds to thatof the rod and becomes quickly bigger tending to assume a sphericalshape due to its surface tension. The edge zone R screens a thin zone ofthe envelope against the radiant heatof' the molten bath. Therefore, inthis zone 78 the envelope is gasifled somewhat regularly and moreoverthedrop absorbs some carbon at this point. Since, however, the thicknessof the envelope considerably overhangs the edge zone of the drop, whichamounts to 0.2 mm. at most, a large portion of-the envelope is exposedto the 5 entirely irregular radiant heat of the molten bath. It istherefore gasified irregularly, and under the formation of projectionsand irregular shapes. provides a gas jet which gives off a certainamount of gas in quite uncontrolled radia- 10 tion. a major part of thismerely polluting the workshop. Moreover, the gas radiation obtainablefrom the edge zone R is disturbed by this uncontrolled radiation.Therefore, such electrodes will only give slightly improved results over16 and above the older arrangements in the case of quite regular formsof baths, e. g. when welding a simple seam.

' The same applies to an electrode constructed according to Fig. 2. Thisalso illustrates a known 20 arrangement. The electrode is first of allsurrounded by a layer of textile material, e. g. a woven tube 11', andis then immersed into a slag forming mass ofknown kind. Sometimes alloymaterial, such as ferro-manganese, is added to 25 these masses. Theforegoing arguments show why this addition is practically useless, sincein the immediate vicinity of the rod, where the drop would be capable ofdissolving the alloy material in the zone R, none or only a small partof the material is present. The evolution of the protective gas may be alittle more regular, since it is directed by the outer side of the slagenvelope. Due to the penetration by such slag, however, it becomes againirregular and moreover the thick envelope of slag is not stable enoughand does not form a sumciently regular shape to enable the directing ofthe gas jet.

Figs. 3 and 4 show the new electrode. As shown in Fig. 3, the electroderod ishelically wound with a paper band P as mentioned above. The bandcarries a layer of alloy material indicated at M and presses same on tothe rod E. D is the envelope which is intended to give the retortaction, as has been termed in the descrlption. R is again the edge zoneof the molten drop T and S is the edge zone of the bath. In Figs. .3 and4 the layers of the envelope are exaggerated in thickness to be shownclearly. As

. already mentioned, Figs.- 1 and 2 are true to'scale,

but in the electrodes according to Figs. 3 and 4 the whole envelope,.comprising the layers M, P and D, is mostly less than /2 mm. thick, asfollows from the thickness of the paper and the thickness of the metallayer indicated above.

As will be seen in Figs. 3 and 4, the whole amount of the alloy materialis in the dissolving zone of the drop, so that it is completelydissolved and transferred into the bath. The gasiflable layer P is sothin that this is also in the screen- 00 ing zone of the drop andtherefore is regularly gasifled. Therefore, the slight amount oi gasevolved from the material may be generated within the thin coating Dwith suflicient certitude as in a retort open towards the bath, and the05 coating D is so little aflected by the slight amount of gas that itextends right down to the active zone and guides the gas jet as aringnozzle in such manner that the small amount of gas forms a tubularjet enveloping the melting area. This gas jet is indicatedatGin Fig.4.

The desiderata of steady and constant alloying of the rod and evolutionof a constant stream of gas which is directed as a tubular jet toenclose the welding bath are thus achieved completely 1 3 than thediflerence between the greatest rndiun oi'themoltendroptormingettheendofthe electrode during welding and the radius of theaaid'inner steel rod. nu external incombustible and non-gulilablemineral cover for the purpose V of bringing the lower end of the band ofcellulose into the lcreening none of said drop.

